PAC RIM ACTIVE: October was wet, but not the wettest

It’s been a pretty wet month, wetter than usual. And quite honestly, I haven’t been out much, other than to watch birds. And I think many people would rather not hear about me blather on about them more than I already do.

So the topic today is rain.

When I was in the tourism business, one of the questions I often got asked is, “How much does it rain on Vancouver Island?

Good question. After all, we live here in a temperate rainforest. And the answer, of course, is “It varies!” But overall, the months with the lowest precipitation are June, July, and August.

I pulled out some precipitation data from the Environment Canada Weather Office site. I selected a few communities from up and down Vancouver Island, and on both the east side and the west side.

The trends are quite interesting. Holberg, on northern Vancouver Island, gets close to four metres, or 12.5 feet, of rain. Wow! That’s a lot of rain! And Tofino, about a third of the way up the Island on the west side gets a similar amount, 3.3 metres or 11 ft.

But Henderson Lake, just down the Alberni Inlet, takes the cake at 6.6 metres or almost 22 ft. of rain a year! All these locations are on the west side of the Island.

The east side of Vancouver Island is much drier. At 0.83 m, Victoria gets only about four centimetres more precipitation a year than Toronto. That’s not much. It’s less than two inches’ difference considering that both cities get less than a yard of rain a year. It’s less than a quarter of what Holberg gets.

About halfway up the east side of the island is Campbell River. It gets more precipitation, about 1.3 m or 4.4 feet. But still much drier than the west side. Port Alberni lies in the middle of the Island at the end of a long inlet or fjord. The precipitation here is about half of Tofino’s, And Tofino is only 80 km away.

How does this compare to, say, a tropical rainforest like Costa Rica? Simply put, the wettest parts of Costa Rica are about as wet as the wettest parts of Vancouver Island. The country receives more than six metres in a year, comparable to Henderson Lake. It rained every day for 359 days in one location. But the driest parts of Vancouver Island are actually drier than the driest parts of Costa Rica.

The lower precipitation levels on the east side of Vancouver Island can be explained by the mountains in the middle of the island. The prevailing winds are from the west. Moisture-laden air is pushed up over the mountains. In doing this, the air temperature drops and the air cannot carry as much water. It falls on the west side, leaving the air drier when it arrives further east.

As the air moves back down the other side of mountain range, it also warms, and its ability to hold moister increases. This of course, is called the rain-shadow effect. The further south you get on the east side of the Island, the more pronounced this effect becomes.

Astonishingly, there is even a species of cactus that grows on the southernmost parts of Vancouver Island and on some of the Gulf Islands.

The driest months of the year are reliably June, July, August and September. Over on the east side of the Island, you can count on it raining less at this time of year than in Toronto at this time of year.

So unless you want to do some winter storm-watching on the west coast, the time to visit is during these months. Isn’t it handy that it coincides with summer vacations?